Workaround for Cray Compilers

[fedepedron]

We've been using D3 as a sub-dependency for SIESTA, and unfortunately the library does not compile with Cray compilers (at least, up to 16.0.1) straight out of the box.

This is not a consequence of the library being wrong, but of Cray being extremely picky on certain things. Thankfully enough, the workaround are simple enough: only two files need minor modifications.

---

First is src/dftd3/output.f90. It seems that Cray does not like the combination of "trim" and "merge" (I tried using only merge and it worked just fine).

@@ -258,8 +258,11 @@ subroutine ascii_damping_param(unit, param, method)
       if (present(method)) then
          write(unit, '(a, "-")', advance="no") method
       end if
-      write(unit, '(a)') &
-         & trim(merge("D3(0)-ATM", "D3(0)    ", abs(param%s9) > 0))
+      if ( abs(param%s9) > 0 ) then
+         write(unit, '(a)') "D3(0)-ATM"
+      else
+         write(unit, '(a)') "D3(0)"
+      endif
       write(unit, '(20("-"))')
       write(unit, '(a4, t10, f10.4)') &
          & "s6", param%s6, &
@@ -275,8 +278,11 @@ subroutine ascii_damping_param(unit, param, method)
       if (present(method)) then
          write(unit, '(a, "-")', advance="no") method
       end if
-      write(unit, '(a)') &
-         & trim(merge("D3(0M)-ATM", "D3(0M)    ", abs(param%s9) > 0))
+           if ( abs(param%s9) > 0 ) then
+         write(unit, '(a)') "D3(0M)-ATM"
+      else
+         write(unit, '(a)') "D3(0M)"
+      endif
       write(unit, '(20("-"))')
       write(unit, '(a5, t10, f10.4)') &
          & "s6", param%s6, &
@@ -293,8 +299,11 @@ subroutine ascii_damping_param(unit, param, method)
       if (present(method)) then
          write(unit, '(a, "-")', advance="no") method
       end if
-      write(unit, '(a)') &
-         & trim(merge("D3(op)-ATM", "D3(op)    ", abs(param%s9) > 0))
+      if ( abs(param%s9) > 0 ) then
+         write(unit, '(a)') "D3(op)-ATM"
+      else
+         write(unit, '(a)') "D3(op)"
+      endif
       write(unit, '(20("-"))')
       write(unit, '(a5, t10, f10.4)') &
          & "s6", param%s6, &
@@ -311,8 +320,11 @@ subroutine ascii_damping_param(unit, param, method)
       if (present(method)) then
          write(unit, '(a, "-")', advance="no") method
       end if
-      write(unit, '(a)') &
-         & trim(merge("D3(BJ)-ATM", "D3(BJ)    ", abs(param%s9) > 0))
+      if ( abs(param%s9) > 0 ) then
+         write(unit, '(a)') "D3(BJ)-ATM"
+      else
+         write(unit, '(a)') "D3(BJ)"
+      endif
       write(unit, '(21("-"))')
       write(unit, '(a4, t10, f10.4)') &
          & "s6", param%s6, &

---

Second is src/dftd3/reference.f90. Here it seems like it's not really allowed to reference the same array with reshape, when that array is also a parameter. Curiously enough, this can also be fixed by removing reference_cn from the "public" statement, and adding the public tag after the parameter...

       & 0.0000_wp,  2.8878_wp,  0.0000_wp,  0.0000_wp,  0.0000_wp, & ! U
       & 0.0000_wp,  2.9095_wp,  0.0000_wp,  0.0000_wp,  0.0000_wp, & ! Np
       & 0.0000_wp,  1.9209_wp,  0.0000_wp,  0.0000_wp,  0.0000_wp],& ! Pu
-      & shape(reference_cn))
+      & (/max_ref,max_elem/))


    real(wp), allocatable :: reference_c6(:, :, :)

---

I hope you find this useful :)

[awvwgk]

Thanks for reporting. I believe those might be worth reporting to Cray as compiler bugs. Happy to accept a patch in dftd3 as well for making it compatible with Cray.